Deflection yoke for cathode ray tube



y 1956 H. w. LORD 2,748,324

DEFLECTION YOKE FOR CATHODE RAY TUBE Filed on. 26. 1951 Fig. I. 14 M /(Z FZ {E F2 Fig.3

VERTICAL W SWEEP cmcun' Inventor: HORIZONTAL Harold w Lord,

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United States Patent 12 DEFLECTION Yoroa FOR CATHODE RAY TUBE Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 26, 1951, Serial No. 253,241

2 (Ilaims. (Cl. 317-200) My invention relates to cathode ray tube deflection systems'and, more particularly, pertains to a novel deflection yoke comprised of a frame-type, laminated magnetic core and four coils, the convolutions of each of which encompass one leg or side of the core. As used herein, the term frame-type is intended to include cores of rectangular as well as annular shape.

An object of the present invention is to provide a deflection yoke that is simple and inexpensive to construct and yet is entirely efficient in operation.

Another object of the invention is to provide a deflection yoke which includes an improved shield structure.

Briefly stated, a deflection yoke in accordance with the present invention comprises a frame-type magnetic core formed of a plurality of contiguous sections. These sections have at least two pairs of adjacent end portions that are disposed on opposite sides of a plane which intersects the frame. The yoke further includes a plurality of coils, each of which has convolutions that bridge the junction formed by one pair of adjacent end portions. The coils are poled to provide, in the presence of a common energizing signal, individual magnetic field components directed across the ring in the same polarity sense relative to one another.

According to another feature of the invention, a frametype shield of electrically conductive, non-magnetic material encloses the core. The shield includes a plurality of similar contiguous sections that overlie respective ones of the core sections. As in the case for the core sections, adjacent end portions of the shield sections are received by convolutions of one of the coils.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a side view of a cathode ray tube having mounted on its neck portion a deflection yoke constructed in accordance with the present invention; Fig. 2 is a sectional view on an enlarged scale taken along line 22 of Fig. 1; Fig. 3 is a perspective view, in exploded form, of a portion of the yoke shown in Figs. 1 and 2; Fig. 4 is a crosssectional view taken along line 44 of Fig. 2; and Fig. 5 is an electrical circuit diagram, partly in block form, of a complete deflection system including a yoke in accordance with the invention.

Referring now to Fig. 1, a cathode ray tube 10, there represented, includes within its neck portion 11 an electron gun 12 for projecting an electron beam upon a fluorescent viewing screen or face 13. The constructional details of such a tube are generally well known, constitute no part of the instant invention, and hence a further description is deemed unnecessary. In order to deflect the beam from gun 12 across the surface of screen 13, there is provided a deflection yoke 14, con- 2,748,324 Patented May 29, 1956 structed in accordance with my invention, encompassing the face-end of neck 11.

As may be best observed in Fig. 2, wherein neck 11 is shown in dash-dot outline, yoke 14 is comprised of a core having four similar, contiguous, L-shaped sections 15-18. Each section is composed of a group of L- shaped laminations of magnetic material, such as soft iron, which, as shown in Fig. 3, are stacked upon one another to provide a core of suitable thickness. The core sections include adjacent end portions 15a and 16a, 16b and 17b, 17a and 18a, 18b and 15b which occur in one set of pairs, designated by the same letter references a, disposed on opposite sides of a plane that intersects rectangular frame 1518. Another set of pairs, designated by the letter references b, are disposed on opposite sides of a plane which intersects the frame and is transverse to the first-mentioned plane.

The yoke also includes a plurality of coils, the convolutions of each of which envelop one side of rectangle 15-18. Specifically, one coil 19 has turns encircling one leg of the rectangle, as shown in Fig. 4, and it has an axial length approximately equal to the length of that leg. The convolutions of coil. 19 thus receive one pair of adjacent end portions 15a, 16a of the core to bridge the junction formed by these end portions. Similarly, each of the remaining coils 2022 is positioned at one of the other sides of the core and bridges a respective one of the junctions 16b, 17b; 17a, 13a; and 18b, 15b.

A frame-type shield 23-26 of electrically conductive, non-magnetic material, such as copper or brass, encloses core 152-18 and is comprised of four similar, contiguous, L-shaped sections. As illustrated in Fig. 3, wherein section 23 is shown, the shield sections are of channel configuration having inwardly turned lips 27. Thus, each of the shield units receives its associated core section to maintain the laminations thereof in place. Since the shield sections 2326 overlie. respective ones of the core sections 15-18, they have corresponding pairs of adjacent end portions that are bridged by the convolutions of the coils.

A rectangularly shaped, flanged, retaining band 28 receives the core-shield-coil structure just described. It is press-fit in place and serves to clamp the several yoke elements into a locked assembly.

In constructing the deflection yoke, two pairs of coils 19, 21 and 20, 22 are wound upon rectangular mandrels which have a configuration corresponding to that of the core legs. These mandrels are removed after completion of the coils. Next, L-shaped laminations arestacked in four groups (15, 16, 17 and 18) to a thickness corresponding to the required axial dimension of the yoke and each group is placed within one of the four L-shaped shields 23, 24,. 25 and 26. This stage of the assembly process may best be understood from an inspection of Fig. 3.

Thereafter, one leg of each of the L-shaped core-shield sections 15, 23 and 16, 24 is inserted in one end of coil 19 and pressure is applied until ends 15a and 16a meet. The same steps are performed with core-shield sections 17, 25 and 18, 26 and coil 21. Each of coils 20 and 22 is placed on one of the remaining legs of one of these sub-assemblies and the other sub-assembly is similarly employed to complete the yoke structure shown in Fig. 2. Finally, clamp 28 is forced tightly over the unit to lock the several elements in place.

It is apparent from the foregoing description that yoke 14 may be quickly and easily assembled. Moreover, all of the core sections are of identical configuration as are the shield sections. Hence, the deflection yoke in accordance With my invention is simple and inexpensive to construct.

In addition, the yoke is entirely symmetrical about intersecting planes which are parallel to the yoke sides. As a result, the two field components, produced in response to energization of the coils are transversely oriented relative to one another and field distortion is materially less than in an arrangement that does not provide such field-component orientation.

Referring now to Fig. 5, wherein the yoke is shown in schematic form, the circuit there represented is a complete deflection system such as might be employed in a television receiver. The system includes a vertical sweep circuit 29 and a horizontal sweep circuit 30. Coils 19 and 21 are connected in series and to the outpt circuit of unit 29 and coils 20 and 22 likewise are in series and connected to circuit 30.

Coils 19 and 21 are poled to provide, in the presence of a common energizing signal, individual magnetic field components directed across rings 1518 in the same polarity sense relative to one another. The resulting deflecting field, with signals from circuit 29, deflects the beam of tube lengthwise or vertically with respect to the sheet of the drawing. The coils 20 and 22 are similarly poled so that the deflecting field resulting from the application of signals thereto affects beam deflection in a horizontal direction or transverse to that produced by coils 19 and 21. Thus, through the use of vertical and horizontal sweep signals of conventional saw-tooth wave form, a rectangular raster may be developed on viewing screen 13 in a well known fashion.

Since the butt joints 15a, 16a; 16b, 17b; etc. are bridged by respective ones of the coils 19-22, they do not distort the resulting magnetic field. This may be seen by considering one pair of coils 20 and 22, for example. Butt joints 16b, 17b and 18b, 15b are within the convolutions of these coils. Under this physical condition there is very little fringing flux and the internal joints cause no distortion of field.

Because of the opposite polarity of the resulting magneto-motive force of the coils with respect to each other, the remaining joints 15a, 16a and 17a, 18a, which are external to the coils, are essentially at points of zero magneto-motive force. Consequently, no flux exists at these points, and there is none to distort.

Since there is no field distortion, there is no tendency for leakage flux to occur at any of the several butt joints of the core. As a result, the small gaps which might exist at the butt joints of shield 2326 do not detract from efficient shielding of the yoke.

Although in its preferred form the deflection yoke in accordance with my invention has been described as of rectangular configuration, it is also possible to utilize other forms. For example, the core may be composed of four similar, arcuate sections which define a circular or elliptical figure. In this case, the assembly process would be somewhat more involved than for a rectangular core. It would be necessary to move the coils around the yoke so as to permit fitting of the core parts together. Thereafter, the coils would be displaced to positions bridging the several junctions of the core.

While I have shown a particular embodiment of my invention, it will, of course, be understood that I do not wish to be limited thereto since various modifications may occur to those skilled in the art, and that I contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A deflection yoke for a cathode ray tube comprising a frame-type magnetic core including four similar L-shaped contiguous sections having four pairs of adjacent end portions, a plurality of coils, each having convolutions receiving one of said pairs of adjacent end portions to bridge the junction formed by said portions in said one pair of portions, oppositely disposed pairs of said coils being poled to provide, in the presence of a common energizing signal, individual magnetic field components directed across said frame in the same polarity sense relative to one another, and a frame-type shield of electrically conductive non-magnetic material including four similar L-shaped contiguous sections, each overlying one of said L-shaped sections of said core and received at least in part by the convolutions of the coils associated with the core section.

2. A deflection yoke for a cathode ray tube comprising a frame-type magnetic core including four similar L- shaped contiguous sections having four pairs of adjacent end portions, a plurality of coils, each having convolutions receiving one of said pairs of adjacent end portions to bridge the junction formed by said portions in said one pair of portions, oppositely disposed pairs of said coils being poled to provide, in the presence of a common energizing signal, individual magnetic field components directed across said frame in the same polarity sense relative to one another, and a frame-type shield of electrically conductive non-magnetic material including four similar L-shaped contiguous sections of channel configuration, each receiving one of said L-shaped sections of said core and received at least in part by the convolutions of the coils associated with the core section.

References Cited in the file of this patent UNITED STATES PATENTS 1,548,022 Casper et al Aug. 4, 1925 2,221,983 Mayer et al Nov. 19, 1940 2,229,977 Kenyon Jan. 28, 1941 2,239,865 Urtel Apr. 29, 1941 2,383,308 Hansen Aug. 21, 1945 2,395,966 Goldberg Mar. 5, 1946 FOREIGN PATENTS 321,042 France Dec. 27, 1902 750,218 Germany Jan. 4, 1945 

